Vehicles such as fork lift trucks are in wide use for handling and moving articles between various locations. In the operation of these vehicles it is often required that the vehicle be simultaneously steered and driven at various speeds, as well as having the forks actuated to pick up or deliver articles. The steering of the vehicle and the manipulation of the forks are normally controlled by the operator's hands, while the direction and speed of the vehicle are controlled by the operator's feet. Since all of these operations could occur simultaneously, various control arrangements have been developed to simplify the work required by the vehicle operator.
Typically, the prior art uses pedal arrangements that enable the operator to shift the vehicle transmission between neutral and forward or reverse drive while at the same time accelerating the vehicle engine. Additional pedal arrangements are utilized to provide inching control, known as vehicle "creep", in which the engine is run at a high speed with the transmission near its neutral position to allow, for example, slippage of transmission clutches. In one pedal arrangement, pedal members or portions are spaced closely together, in which one member controls engine speed and another the position or drive condition of the transmission. A problem exists in that to produce creep the engine speed is at a relatively high r.p.m. before starting to engage the transmission, and this could cause, for example, transmission clutches to prematurely burn up. In another pedal arrangement, the pedal members employed for producing creep are widely spaced so that the operator disadvantageously has to use both feet for this purpose, unlike the one arrangement.
Furthermore, the prior vehicles typically incorporate a "dead-man" feature which prevents the transmission of power from the engine drive shaft to an output driven shaft and, hence, vehicle movement. This "dead-man" function can be obtained by automatically shifting a transmission control lever or valve from a forward or reverse drive condition to neutral when the operator leaves the vehicle. However, due to a malfunction, the lever or valve may not be returned to neutral, whereby the vehicle can still be moving even with the operator removed from the vehicle.
Also, the prior art utilizes override mechanisms which enable a pedal member to be further depressed after shifting a transmission into drive in order to increase the speed of the engine. The mechanisms typically include springs which are preloaded to permit full movement of, for example, a transmission control lever upon partial movement of the accelerator pedal member, and which are then compressed upon further movement of such a pedal member without moving the control lever. A problem with these override mechanisms is that the spring can wear or fatigue after a period of use in which they are constantly compressed and uncompressed, whereby they will need to be replaced. Another problem with such prior override mechanisms is that the force required to compress the springs is substantial, thereby requiring great effort by the operator.